I was asked to help out with planning a study of cancer survival based on transcriptome analysis. As part of that, the PI has requested a power analysis. We will be able to enroll 300 subjects over three years, with an additional year of follow-up and minimal to no losses to follow-up. However, there is no reasonable way to estimate survival times or hazard ratios for the two groups, as the groups will not even be defined until at least mid-way through the study, so anything I enter for GROUPMEDSURVTIMES or HAZARDRATIO (or similar) would be making numbers up entirely out of thin air. Instead of a "typical" power analysis, i.e. estimating how many subjects needed (or the expected power given the number of subjects), I am wondering if it is possible to instead estimate the hazard ratio given the sample size, 1:1 allocation, power of 0.8, and duration of study. From the documentation it appears that HAZARDRATIO is not amenable to this, but I'm hoping there is a workaround or some other means of generating something useful. PROC POWER;
TWOSAMPLESURVIVAL TEST = LOGRANK
HAZARDRATIO = .
ACCRUALTIME = 3
TOTALTIME = 4
NTOTAL = 300
POWER = 0.8
;
RUN;
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